JPH023530B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention uses an electrolyte that exhibits excellent copper ion conductivity, and aims to provide electric double layer capacitance application devices such as low-loss capacitors and potential storage devices with a wide operating current range. do.

Conventionally, there are silver ion conductors in which AgI is partially substituted with anions, cations, or mixed anions and cations as substances that exhibit high ionic conductivity at room temperature. Batteries using this, electric double layer capacitors, and display elements using WO ₃ have also been developed, but since they are mainly composed of silver and silver salts, they are expensive and have not been widely used.

In response, attempts have been made to use copper ion conductors, but the materials that have been obtained so far that exhibit high ionic conductivity use organic materials, so they have low heat resistance or high temperature However, it had the disadvantage of having a narrow practical temperature range due to its high electronic conductivity.

In contrast, the inventors replaced 1/5 of the Cu ⁺ ions in CuCl with Rb ⁺ , K ⁺ , NH ₄ ⁺ , and NR ₄ ⁺ and 1/3 of the Cl ^- ions.
We have already found that a material with ~1/4 mixed substitution with I ^- ions exhibits relatively high Cu ⁺ ion conductivity at room temperature and also has a relatively wide practical temperature range.

The present invention replaces Cu ions with Rb ⁺ , K ⁺ ,
Rb ⁺ and K ⁺ than NH ₄ ⁺ , NR ₄ ⁺ ions alone
This was based on the discovery that replacing cations with two types of cations has higher ionic conductivity, lowers internal resistance when used in devices such as batteries, and allows even larger currents to flow. It is.

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 first describes the electrolyte used in the present invention. KCl, RbCl, CuCl, and Cul, which had been heated in advance at 140°C in air for 2 hours, were mixed in a mortar at a ratio of MeCu ₄ I _1.5 Cl _3.5 . Only Rb as Me (conventional) and mixture of K and Rb (invention)
was used. These mixtures were press-molded into pellets, placed in a sealed glass container, the inside of which was evacuated, and then heated at 250° C. for 17 hours to cause a reaction. When the product was subjected to X-ray diffraction, a substance completely different from the raw material was formed as shown in Figure 1, and it was confirmed that this crystal had the same structure as the conventional RbCu ₄ I _1.5 Cl _3.5 . Further, the relationship between the composition, lattice constant, and room temperature conductivity is as shown in FIG. 2, and the addition of K reduces the lattice constant and increases the conductivity by about 50% in the composition range of the present invention. Since the electron transport number is extremely low as in the conventional case, it is clear that the increase in electrical conductivity is due to the increase in ionic conductivity.

Next, FIG. 3 shows the structure of an electric double layer capacitance applied element using the electrolyte prepared as described above.
In the figure, reference numeral 1 denotes a polarizable electrode, which is made of a mixture of an electrolyte and an electronically conductive material such as carbon/Cu ₂ S, which is electrochemically inert. The differences depending on the electrode material are as follows. When carbon, platinum, palladium, etc. are energized within the voltage range of the electrolyte's decomposition voltage (approximately 0.6V), no electrochemical reaction occurs at the electrode, and the decomposition voltage of the electrolyte can be withstand voltage, but the adsorbed gas Electrochemical reactions occur even below the withstand voltage, so if care is not taken to remove it, it will appear as a leakage current.

Although Cu ₂ S has low leakage current, it has the disadvantage that the voltage range in which electrochemical reactions do not occur is narrow at 0.07V. Reference numeral 2 denotes a current collector for the polarizable electrode 1, which is formed of graphite, platinum, palladium, or gold by vapor deposition or sputtering. 3 is an electrolyte. 4 is the opposite
₂ :3 mixture of Cu2S and Cu, 3:3 of _TiS2 and Cu
7 mixture, or a mixture of Cu ₂ S alone and an electrolyte. These are called non-polarizable electrodes, and the precipitation and dissolution reactions of Cu ⁺ ions are carried out by applying electricity. The mixture electrode has an open circuit voltage close to that of Cu and has better reversibility than the Cu electrode.
The difference is that Cu ₂ S alone exhibits an open circuit voltage of 310 mV. Reference numeral 5 denotes a current collector for the counter electrode 4, and the copper is either press-fitted into the counter electrode 4 as a net or deposited on the counter electrode 4 by vapor deposition. 6 is an electrolyte, and 7 is a reference electrode, in which a mixture of Cu ₂ S and an electrolyte is used. 8 is a current collector of the reference electrode 7, which is made of copper. Note that the electrolyte 6, the reference electrode 7, and the current collector 8 are provided to accurately measure potential changes of each electrode, and are not necessary for a capacitor for obtaining an output.

Using Cu ₂ S for polarizable electrode 1 and a mixture of Cu ₂ S and Cu for counter electrode 4, 0.1 g of polarizable electrode 1 and 0.2 g of other electrodes and electrolyte were collected to form a 10 mmφ cylindrical element. . Figures 4 and 5 show the respective characteristics when the electrolyte of the present invention is used as the electrolyte (shown in area A in the figure) and when an electrolyte for comparison is used (shown in area B in the figure). shows. Fourth
The figure shows the change in potential caused by the current flowing through the polarizable electrode and the change in potential after the current is stopped. When a conventional electrolyte is used, when a current of 20 mA is applied, a potential change occurs, which is thought to be due to a delay in the movement of ions in the electrolyte, and there is a delay in potential rise (a), and a large overshoot (b) and decrease (c) in the potential after the current is stopped. However, this did not occur with the device according to the present invention, and only occurred when 30 mA was applied.

The potential change of the counter electrode was as shown in FIG. 5, and the polarization of the electrode according to the present invention was significantly reduced.
If the polarization of the opposite pole can be ignored, 2
Even in a device with a polar structure, the potential behavior of a polarizable electrode can be indicated by the terminal voltage, and potential storage elements that utilize the linearity of the potential with respect to the current flow capacity of the polarizable electrode and the retention of the potential when the current flow is stopped are developed. It has the advantage that the structure is simple, and that energy loss can be reduced when used as a capacitor for storing and discharging electrical energy.

Although the above example shows an electric double layer capacitor, the difference between a battery and an electrochemical display device using WO ₃ is that a polarizable electrode is not used, but a non-polarizable electrode is used for both electrodes. Therefore, they have exactly the same effect of reducing loss due to energization.

[Brief explanation of drawings]

Figure 1 shows the electrolyte X used in the present invention.
Electrolyte conventionally used in line diffraction diagrams RbCu ₄ I _1.5 Cl _3.5
This is shown in comparison with FIG. 2 is a diagram showing the lattice constant and conductivity of the electrolyte used in the present invention, FIG. 3 is a cross-sectional view showing the configuration of the electric double layer capacitance applied element according to the present invention, and FIG. FIG. 5 is a diagram showing the change in potential of the polarizable electrode of the multi-layer capacitance applied element in comparison with that of a conventional one, and FIG. be. 1... Polarizable electrode, 2, 5, 8... Current collector,
3, 6... Electrolyte, 4... Counter electrode, 7... Reference electrode.

Claims (1)

[Scope of Claims] 1. An electric double layer capacitive element having a polarizable electrode and a counter electrode facing each other, both of which contain an electrolyte, wherein the electrolyte has the chemical formula MeCu ₄ I _2-x.
It is expressed as Cl _3+x (0.25x0.5) and the above Me is 1:
An electric double layer capacitance applied element characterized by using a compound consisting of K and Rb in a ratio of 9 to 1:3. 2. The electrical electrode according to claim 1, wherein the polarizable electrode is made of a mixture of at least one selected from the group consisting of Cu ₂ S, carbon, platinum black, and palladium black and an electrolyte. Multilayer capacitive application element. 3 Counter electrodes are Cu ₂ S + Cu, Ti ₂ S + Cu, and Cu ₂ S
The electric double layer capacitance applied element according to claim 1, characterized in that it is made of a mixture of at least one selected from the group consisting of: and an electrolyte. 4. The electric double layer capacitance applied element according to claim 1, further comprising a reference electrode for accurately detecting potential changes of the polarizable electrode.